means of trees raised from seed in a nursery; but sometimes also by sowing the seed on the ground intended for the plantation; in which case, if circumstances permit, a crop of grain is often sown along with the seeds of the trees, as these do not in general vegetate very soon; and the young plants derive advantage from the absence of choking weeds when the grain-crop is reaped, and from the protection afforded by the stubble. It has been supposed by some, but there is no sufficient evidence in support of the opinion, that more healthy and vigorous trees are obtained by sowing on the spot than by planting those which have been raised in a nursery. However, only very young trees can be planted with advantage, those which have attained a greater size requiring a degree of attention far beyond what is possible in plantations even of very moderate extent. The time of planting is from November to February. The most approved mode of planting is in small pits, in which the roots are disposed in a natural manner, and which are then carefully filled up with earth; but it is often thought sufficient when the tree to be planted is very young, to make a slit for it with the spade, or two slits, one at right angles to the other in the form of the letter T. Ŏther methods are also adopted, particularly for rocky situations, in which the spade cannot be used. Economy is often a consideration of great importance in determining the mode of planting.

The formation of plantations by the sowing of seed has been more generally practised on the continent than in Britain. In this way the vacancies in the natural forests of France and Germany are filled up. In this way also great sandy tracts have been covered with wood on the coasts of Pomerania and of France. This has particularly been accomplished on a scale of extraordinary magnitude in the downs of drifting sand, between the rivers Adour and Gironde. The operations there were begun by M. Bremontier in 1789, and deserve to be mentioned as perhaps the most important operations in A. that have ever been performed in the world. Vast forests of pinaster now occupy what was originally loose sand destitute of vegetation.

Too little attention has hitherto been generally paid to the adaptation of the kinds of trees that are planted to the soil and climate; and to this cause many failures in A. are to be ascribed. Some trees grow well even in exposed situations, and are fit to be employed in these, either to form entire plantations, or to occupy the outer part, and so to shelter other trees, which in general are not planted until the outer zone or belt of the most hardy kinds is somewhat advanced; some succeed only in rich soils; some are incapable of enduring the sea-breeze; others, as the sycamore, the elder, and the pinaster, are comparatively unaffected by it. Some trees suffer from an amount of moisture from which alders or willows would rather derive advantage; but, in general, the thorough drainage of the land intended for a plantation is one of the circumstances most important to its success.

To the necessity of this thorough drainage we must look as compensating, or more than compensating, the influence which woods exercise in condensing the moisture of the atmosphere, and in rendering a climate cold and damp; marshy soils being in this respect still worse. The shelter afforded by plantations judiciously disposed, whether in belts or otherwise, is also of great importance in rendering them suitable for that improved agriculture in which thorough drainage is of the first necessity, and which is always productive of amelioration of climate. The influence of plantations is therefore, upon the whole, beneficial, although vast masses of

forest are injurious to climate; and it must be admitted that in some localities the planting of trees has been carried to excess, so that fields often suffer, particularly in autumn, from want of free circulation of air, and the landscape is often restricted to very narrow limits. The remedy in such cases is obvious; and it not unfrequently happens that within a short distance new plantations might be formed with every prospect of benefit.

Much has been written about the pruning of forest trees, with a view especially to the production of taller and straighter stems; and considerable difference of opinion exists as to the extent to which pruning should be practised. It is, however, very generally delayed till the branches to be removed have attained too great a size, and is then very rudely performed, to the spoiling of the timber rather than to the improvement of it. The practice of leaving snags, instead of cutting_branches clean off, has particularly bad effects. Pines and firs, from their manner of growth, need pruning less than trees of other kinds. When trees have been planted, not merely for profit but for ornament, this ought to be remembered in pruning, which, however, is too often intrusted to persons utterly devoid of taste; and trees which, as they naturally grew, were very beautiful, are so treated with axe and saw that they become deformities instead of adorning the scene.

In forming plantations, different kinds of trees are very generally mixed, although masses of one particular kind are also frequently planted. It is usual, however, to plant along with those which are destined most permanently to occupy the ground, trees of other kinds as nurses, to be gradually removed as the plantation advances in growth. For this purpose, spruce and larch are more generally employed than any other tree; although Scotch fir and birch are also deemed suitable for certain situations. The removal of some of these nurses affords the first returns of profit from the plantation, which is afterwards thinned from time to time. Plantations far more frequently suffer from being thinned too little, than from being thinned too much. To the want of proper thinning is to be in part ascribed the failure of many of those narrow belts of planting which are too common in Scotland, and which having been intended for shelter, very imperfectly serve their purpose, and seem to have suffered from the hardest usage themselves. The thinning of a plantation which has been allowed to grow too thick, must, however, be very gradually performed, that it may be beneficial, and not injurious. After a sudden thinning, a plantation sometimes ceases to thrive, and many trees are often laid prostrate by the next storm; for trees accommodate themselves both in their roots and branches to the situations in which they grow.

A considerable number of years must elapse before any pecuniary return is derived from a plantation, yet this mode of employing soils is often found to be the most remunerative of which they are capable, even without reference to the improvement of adjacent lands to which shelter is afforded; and the increased demand for timber in Britain, for sleepers of railways and other purposes, tends to the still further encouragement of A.

The resinous products of pine-woods are not considered as a source of profit in Britain; but the tar, turpentine, and resin obtained from them in some parts of Europe, form articles of commerce. The great pinaster plantations already mentioned, on the sands between the Adour and Gironde, now yield products of this kind in large quantity. The employment of trees for ornamental purposes belongs not so much to A. as to Landscape Gardening (q. v.). The transplanting (q. v.) of large trees is only practised for

at Hampstead, in 1735. A. was one of the leaders in that circle of wits which adorned the reign of Queen Anne, and was still more nobly distinguished by the rectitude of his morals and the goodness of his heart. He assisted Swift and Pope in the composition of that brilliant satire, the Memoirs of Martinus Scriblerus, contributing those portions of it which refer to science and philosophy; and he was undoubtedly the author of the celebrated political jeu d'esprit, the History of John Bull, which has so often been imitated. Besides several medical essays, he published Tables of Greek, Roman, and Jewish Measures, Weights, and Coins (London, 1705-1708), a work which was long the best authority on the subject. There is also a philosophical poem of his composition in Dodsley's Miscellanies, entitled Know Thyself.

A'RBUTUS, a genus of plants of the natural order Ericea, containing a number of species, small trees and shrubs, the greater part of which are American. The fruit is fleshy, 5-celled, many-seeded, usually dotted with little projections, whence that of some species has a sort of resemblance to strawberries; the corolla is urn-shaped.-A. U'nedo, the

Arbutus Unedo.

STRAWBERRY TREE, is a native of the south of Europe, found also in Asia and America, and in one locality in the British Isles, the Lakes of Killarney, where its fine foliage adds much to the charm of the scenery. It requires protection in winter in the climate of Paris. In Britain, it is often planted as an ornamental evergreen. It grows to the height of 20-30 feet, but is rather a great bush than a tree. The bark is rugged; the leaves oblongo-lanceolate, smooth and shining, bluntly serrated; the flowers nodding, large, greenish white; the fruit globose, of a scarlet colour, with a vapid sweetish taste. It is, however, sometimes eaten. Of late, excellent alcohol has been made from it in Italy. A wine is made from it in Corsica, which, however, is narcotic, if taken in considerable quantity, as the fruit itself is, if eaten too freely. The bark and leaves are astringent.-A. Andrachne is also sometimes cultivated as an ornamental plant in Britain, but is impatient of severe frosts. Its fruit, and that of A. integrifolia, are eaten in Greece and the east. But all the species seem to possess narcotic qualities in greater or less degree; the fruit of A. furens, a small shrub, a native of Chili, so much as to cause delirium.-A. aculeata, which abounds at Cape Horn and on Staten Island, is an elegant and most pleasing evergreen, very much resembling the myrtle. It grows to the height of 3 or 4 feet, and produces small white flowers, followed by a profusion of red shining berries, which ornament the bush during winter.

Their flavour is insipid, but somewhat astringent. Mixed with a few raisins, they have been made by voyagers into tolerable tarts.-A. Uva ursi, now generally called Arctostaphylos Uva ursi, the RED BEARBERRY, is a small trailing evergreen shrub, common in the Highlands of Scotland and in the Hebrides, and indeed in the northern parts of Europe, Siberia, and North America. It grows in dry, heathy, and rocky places. The flowers are in small crowded terminal racemes, of a beautiful rose colour. The berries are austere and mealy; they are said to form a principal part of the food of bears in northern regions. Grouse also feed on them. The dried leaves are used as an astringent and tonic medicine, and as such have a place in the pharmacopoeias, being principally employed in chronic affections of the bladder; but those of Vaccinium Vitis Idea are often fraudulently substituted for them.-The BLACK BEARBERRY (A. or Arctostaphylos alpina) is also a native of the northern parts of the globe, a small trailing shrub, with black berries about the size of a sloe, relished by some, but having a peculiar taste, which to others is disagreeable. The plant is found on many of the Highland

mountains of Scotland.

ARC (Lat. arcus, a bow) is any part of a curved line. The straight line joining the ends of an A. is its chord, which is always less than the A. itself. Arcs of circles are similar when they subtend equal angles at the centres of their respective circles; and if similar arcs belong to equal circles, the arcs themselves are equal. The length of an A. is readily found if the angle which it subtends at the centre of the circle is known, and also the length of the whole circumference. Let the whole circumference be 100, and the angle of an A. 50°, the length of the A. is 100 × 50 360° 50°:: 100: 14 nearly. 360 ARC. See JOAN OF ARC.

=

ARCA, or ARK-SHELL, a genus of bivalve shells, and lamello-branchiate mollusca, the type of a family called Arcada, or Arcaceae. In the true ark-shells, the hinge is straight, and occupies what at first seems the whole length of the shell, but is in reality its whole breadth, the breadth being greater than the length. One species is found on the British shores; the species are larger and more numerous in the seas of warmer climates, and some of them are frequently to be seen among the shells employed for the ornament of drawing-rooms, &c. Fossil Arcade are, however, more numerous than recent species, and are found in various rock systems.

ARCA'DE (Fr.), a row of arches, supported by columns, either having an open space of greater or less width behind them, or in contact with masonry. The A. in Gothic corresponds to the colonnade in classical architecture, the difference between them being that, whereas the pillars in the colonnade support straight architraves, those in the A. support arches. The term A. is sometimes applied to the row of piers, or columns and arches, by which the aisles are divided from the nave of a church, or by which cloisters, or what are erroneously called piazzas in Britain, are enclosed; but it is more generally confined to those series of smaller arches which are employed simply for purposes of ornamentation. Arcades of the latter kind are often found surrounding the square towers of English churches. Of this we have early examples in the church of Middleton Stoney, Oxfordshire, and in the still older ones of Tewkesbury, and Christ Church in Oxford. The term is also applied, improperly, to a glass-covered street or lane, with a row of shops or stalls on each side.

ARCA'DIA, the middle and highest part of Peloponnesus, was bounded on the N. by Achaia, on

the E. by Argolis, on the S. by Messenia and Laconia, and on the W. by Elis. According to Pausanias, it derived its name from Arcas, the son of Callisto. Next to Laconia, A. was the largest country in the Peloponnesus. It had an area of 1700 square miles, and was girt round by a circle of mountains, which cut off to a large extent its communication with the rest of the peninsula. Mountains also intersected it in different directions. The western part of what was anciently A., is wild, bleak, and rugged, and was at one time covered with huge forests; the eastern is more fertile, the mountains not so high, and the vales more luxuriant. In these eastern valleys lay all the principal cities of A. The loftiest peak in A.-the loftiest also in the Peloponnesus-is Mount Cyllene, in the northeast (778 feet). The chief river was anciently the Alpheius (q. v.). Originally A. was named Pelasgia, after its first inhabitants, the Pelasgi. Subsequently, it was divided into several small states, which formed a confederation. Of these united states, the chief were Mantinea, Tegea, Orchomenos, Pheneus, Psophis, and Megalopolis. The inhabitants, engaged chiefly in tending cattle and in hunting among the wild highlands, remained long in a state of barbarism. After civilisation had advanced, and the Arcadians had become known by their love of music and dancing, they still retained some military spirit, and were sometimes engaged as mercenary soldiers. But generally their character accorded with their simple, rural mode of life; though it seems certain that human sacrifices were offered as late as the period of the Macedonian sway. The Arcadians were not remarkable for their intelligence. In fact, an Arcadian youth' was a synonym for a blockhead. Pan and Diana were their favourite deities. Ancient and modern poets (the latter especially in the time when pastorals' were popular) have described A. as the land of peace, innocence, and patriarchal

manners.

ARCA'DIUS, first emperor of the East (395-408 A. D.), was born in Spain, 383 A. D., and was the son of the Emperor Theodosius, after whose death the Roman empire was divided into East and West. A. lived in oriental state and splendour, and his dominion extended from the Adriatic Sea to the river Tigris, and from Scythia to Ethiopia; but the real rulers over this vast empire were, first, the Gaul Rufinus, and afterwards the eunuch Eutropius, who openly assumed the reins of government and the command of the army, while A. reposed in luxurious indifference. In 399, the eunuch Eutropius was deposed by another usurper, Gainas, who, in his turn, soon fell a victim to his own ambition. After wards, Eudoxia, the wife of the emperor, assumed the supremacy. One really great man adorned this period, the virtuous and eloquent Chrysostom, who was persecuted by Eudoxia, and through her influence exiled in 404, on account of his firm opposition to Arianism, which the empress herself favoured. During the reign of A., his territories suffered by barbarian incursions, earthquakes, and famine, but nothing could disturb the indifference of the monarch. He died, unlamented, 408 A. D.

ARCESILA'US, a Greek philosopher, founder of the New Academy, was born at Pitane in Æolia, Asia Minor, 316 B. C. He studied philosophy, first under Theophrastus the Peripatetic, and afterwards under Crantor. After the death of Crantor, A. became the chief master of the Academic party, or those who held to the doctrines of Plato; but he introduced so many changes that its philosophic character was completely changed. His great rivals were the

Stoics, whose opinions he attacked, but he does not appear to have attained any certainty in his own convictions. He had studied under too many masters, and discussed too many different systems, to be sure of the truth of any. He denied the Stoical doctrine of a 'convincing conception,' which he affirmed to be, from its very nature, unintelligible and contradictory. He also denied the existence of any sufficient criterion of truth, and recommended abstinence from all dogmatic judgments. In practice he maintained that we must act on grounds of probability. It is not easy to determine satisfactorily what his moral character was. A wit, a poet, and a man of frank and generous disposition, which seems to have captivated his disciples even more than his philosophy, he has yet been accused by his enemies of the grossest profligacy; and whatever extravagance there may be in such an extreme charge, it is tolerably certain that he died of a debauch in his 76th year (241 B. C.). Nevertheless, his adversary Cleanthes, the Stoic, passed this high eulogium on him: "The morality which A. abolishes in his words, he re-establishes in his actions.'

ARCH, an arrangement of bricks, stones, or other materials over an open space, by which they are made not only to support each other by mutual pressure, but to sustain a superincumbent weight. We have the excellent authority of Sir G. Wilkinson for stating that the A. was known to, and used by, the ancient Egyptians; and that the Assyrians were acquainted with its principles is placed beyond doubt by the arched gateways so frequently represented in their bass-reliefs. The A. is generally supposed to have been unknown to the Greeks-a supposition which becomes very improbable if we hold it to be proved that it was used by nations with whose works they must have been familiar. But that the Greeks did not employ it generally in their architectural structures, is certain; and as it is not less certain that the Romans did, it is to the latter people that the nations of modern Europe are indebted for their acquaintance with its great utility. The introduction of the A. by the Romans gradually effected a complete revolution in the architectural forms which they borrowed from the Greeks. The predominance of horizontal lines gave way by degrees, till, as the Romanesque passed into the Gothic style, it was superseded by the segments of a circle, placed generally more or less in a perpendicular direction. In its earliest application by the Romans, the A. did not spring from the entablature of the columns, but was generally placed behind them, and rested upon separate imposts. Subsequently, this arrangement was departed from, and the A. assumed the position which it has since retained above the columns; sometimes having an entablature interposed, and sometimes rising directly from the capital of the column or pier, as in the Romanesque. Before mentioning very briefly the different forms of the A., it seems natural to refer to a very simple structure, frequently met with in those early edifices in our own country which we are in the habit of designating as Saxon. It consists of two stones, their lower ends resting on rude piers, their tops leaning against each other, and thus forming two sides of a triangle, which is capable of supporting a moderate superincumbent weight. The mechanical principles on which the A. depends, though here very imperfectly employed, seem sufficiently called into play to suggest their more extensive application; and it is not impossible that out of this rude construction the A., in its later and more elaborate forms, might have developed itself amongst ourselves without hints from foreign sources.

Of the A. itself, the following variations of form